Thread-cutting mechanism for sewing machines



- Sept. 20, 1932. Y A. F. FIFIELD 1,818, 80

THREAD CUTTING MECHANISM FOR SEWING MACHINES Filed D80. 20, 1950 4 Sheets-Sheet 1 Sept. 20, 1932. Q FlFlELD 1,878,430

THREAD CUTTING MECHANISM FOR SEWING MACHINES Filed Dec. 20. 1956 4 Sheets-Sheet 2 Sept. 20, 1932. F, FlFlELD v lfi'igfi i) THREAD CUTTING MECHANISM FOR SEWING MACHINES Filed Dec. 20. 19:50 4 Sheets-Sheet 5 Sept. 20, 1932. FlFlELD 1,878,480

THREAD CUTTING MECHANISM FOR SEWING MACHINES Filed Dec. 20, 1930 4 Sheets-Sheet 4 Patented Sept. 20,:1932

I UNITED STA ALBERT IE. rrrinrnior NEWARK, new JERSEY, Assrenon TQTHE smear. MAn rnc TUBING COMPANY, or ELIZABETH, new JERSEY,'A CORPORATION or n nwannsnv THREAD-CUTTING M ECHAN ISM ron snwme MAonINEs Application filed December 20, 1930. Serial No. 503,699.

7 This invention relates to sewing machines, more particularly of the loclcstitch cylinderbed type adapted for the sewing on. of shank buttons, and has for an object to provide a simplified mechanism for severing both the needle and bobbin-threads of such a machine: Another object of the invention is to simplify the thread-cutting mechanism disclosed in the patent to Barron et al., No. 1,336,808,

v of April13, 1920..

To theattaimnent of the ends in view the invention comprises the devices, combinations and arrangements of parts hereinafter described and claimed;

The features of the invention and the advantages attained thereby will be readily understood by those skilled in the art from the following detailed description of' a specific embodiment of the invention illustrated in the accompanying drawings,vin which Fig. 1

is a front side elevation of a shank-button sewing machine embodying the invention. Fig. 2 is a reverse side elevation of the machine. Fig. 3 is a rear end elevation of the machine. Fig. 1 is a front end elevation of the work-holding and stitch-forming devices. Fig. is a plan view of the free end of the work'supporting arm of the machine with the throat-plate removed to show the thread-cut-v ting devices. Fig. 6 is a similar View with the thread-cutting devices in thread-cutting position. Figs. 7, 8 and 9 are a series of views showing successive stages in the handling of the last needle-loop prior to the actual severing of the needle and bobbin-threads. Fig.

is a perspective view of theunder side of the throatrpiate. Figs. 11 and 12 are vertlcal sections through the sewing point, taken longitudinally of the work-supporting arm and 1. showing the thread-cutting devices in their initial and in their final positions. 13 is an enlarged vertical. sectional view taken on the line 1313, Fig. 6. Fig. 1 1 is a section through the fulcrum of the automatically actuated lever for the needle-loop severing im,

' tutlng,

. or knee-shift, not shown.

plement, shown in Fig. 1. Figs. and 16 are TIES}. PATENT orrice' L perspective viewsof the stop-motion control mechanism of the machine. Fig. 17 is a view of a portion of the mechanism 'shown in Fig, lat a different time inthecycle of operations, and Fig. 18 isa section on the line 18 1 8, Fig. 6;

Except for certain modifications hereinafter pointed out, the machine illustrated is constructed substantially in accordance with the'disclosureof the Barron et al. patent referred to.

.The frame oftlie machine com prises the standard 1, cylinder-bed 2, and

overhanging bracket-arm ,3 terminating in the head 4;jin whichis mountedithe laterally vibrating needle-bar 5 and spring-pressed resser-bar 6' carrying, respectively, the needle 7 and presser-foot 8. I The pr'esser-bar 6 also carries the.usual'button-clamp 9v having the separable jaws 10 which grip the shank 11 of the button 12 and hold it in stitch-receiving position upon the fabric 13' held by the presser-foot 8 upon the throat= plate 14, which parts 8 and 14 constitute a cloth-clamp orwork-holder. The pressure-l bar has fixed thereto the usual lifter-block 15 under the shoulder 16 of which extendsthe lifting lever 181fulcrumed at 19 and constimechanism for. opening the work-holder for the insertion andremoval of work. ,In prac-' tice, there is secured to the lever'lSby screws 3 20 and arm 21 the rearwardly disposed free end of which is connected to a suitable treadle The-needle 7 cooperates with the usual oscillatory shuttle 21, including the thread- 7 case 22 carrying the bobbin 23, Fig. 4:, to form; stitches; the needle and shuttlebeing'actu ated by the usual connections with the mainin this instance, manually operatedl end17of the manually operated presser-ba'r shaft 24. The main-shaft alsodrives the" V cross-shaft 25 to which is fixed the stopmotion controlling cam 26 and the needleebar vibrating cam 27. The shaft 25 is driven at a slow speed and ordinarily makes one revolution for each button-sewing cycle. In the present instance, how-ever, controlling means are provided whereby the shaft 25 may, at the will of the operator, be caused to make two revolutions before the machine is automatically brought to rest, thus doubling the carries the usual belt-shipper 33 and in-.

cludes the forwardly extending arm 34 which is connected'by the'pulLrod 35 to a suitable v starting treadle or knee-shift (not shown). The arm 34 of the stop-motion lever '32 carries a roller-stud 36 whichis embraced by the forkedarm'37 of abell-crank lever the other I arm 38 ofwhich carries a roller-stud 39 resting in the notch 40 in the cam 26 when the machine is at rest. s

When the stop-motion; lever 32 is tilted to running position, Fig. 15, by a down-pull on the starting rod 35, it is retained in such position by engagement of the hooke'dend 41 of the spring-pressed latch-arm 42 with the arm-43 which is rigidly mounted upon and constitutes a part of the stop-motion lever 32. By this movement of the stopmotion lever 32,the roller 39 is moved outwardly from the notch 40in the stop-motion controlling disk or cam 26. There is mounted on the cam '26 atripping-plate 44having an I inclined nose 45 adapted to strike the tailpin 46' of thelatch-lever 42 and deflect such tailpin inwardly, thereby withdrawing the hooked end 41 of the latch-lever from the arm 43 and'releasing the stop-motion lever 32 for movementto stopping position under the influence of its spring 47, "Fig. 2. The

tripping-plate 44 is sotimed upon thecam 26 that when its nose 45"engages the tail-pin 46 to release the stop-motion lever 32, the trailing end of the notch 40 has just passed the roller 39 and is in the position shown in.

Fig. 16. Thus, althou'ghthe stop-motion lever '32has been released from the hold of the latch-lever 42, it cannot move to stopping osition but is retained in running position iiy the roller 39 riding upon the circular portion of the periphery of the cam 26.11",

" therefore, the operator pulls down on the rod 35 to start the machine/and holds the rod down until the tripping-nose '45 passes' the tail-pin 46, the latch-lever 42, initsrecovery,

will re-engage the stop-motion lever 32 and hold it in running position for one revolution of the cam 26. At the end of the first revolution of the cam 26, the latch-arm 42 "will be tripped by the tripping nose 45 and the roller 39 will be permittedto ride upon the. circular portion of the'peripheryof the cam 26 to retain the stop-motion lever 32 in running position during the second revolution of the cam 26 at the end of which the roller 39 will drop into the notch 40' and permit the stop-motion lever 32 to return to stopping position, (shown in full lines in Fig. 2). The tripping-plate 44 is secured to the cam disk 26 by means of two screws 48, 49. The screw 48 passes through a slot 50 in the trippingplate 44 to permit adjustment of the trip ping-plate 44 about the screw 49 as a center. Inasmuch as the screw 49 is located close to the axis of the shaft 25, the adjustment provides fortheaccurate timing of the tripping nose 45 upon the cam 26.

The bobbin-thread pulloff and severing device, per se, is constructed substantially in accordance with the disclosure of the Barron et al., patent referred to. It comprises a reciprocatory bar 51 mounted on top of the work-supporting arm 2 and carrying at its forward end the vertically spaced cutter and pull-oft blades 52-and 53, respectively. A stafrom its inoperative position, Fig. 11, to its operative position, Fig. '12, thepull-off blade 53 engagesthe bobbin-thread Z2 and passes under the stationary blade 54, thereby forming abight in the bobbin-thread and pulling a length thereof from the bobbin 23. The cutter-blade 52 passes over the stationary blade 54 and, being considerably shorter than the pull-offblade 53 does not engage and sever the bobbin-thread until after the pull-oft movement is practically completed. The bar 51 isconnected by the link 55 to the bell-crank lever 56 which latter is connected by the link .57 to the rearward end of the lever 18 lying behind the stop-motion controlling cam 26. The bobbin-thread pull-oil v and severing device is thus connected to the work-clamp opening mechanism. and is manually operated by the same means whichopens the workclamp. 1 1

An interlocking device is provided to prevent the opening of the'work-clamp while the stop-motion lever 32 is in running position and to prevent the shifting of the stop -motion lever to running position 1 while the workclamp is open. This device comprises a link 58,:Fig. 2, fulcrumed at its upperend at 59 on the sewing machine frame and connected downwardly extending arm 61 rigidly mounted on the stop-motion lever 32. When the stop -motion lever is shifted to running or dot ted line position, Fig. 2, the link 58 is engaged by a roller-stud 62 on the bell-crank lever 56 and blocks the motion of the bell-crank lever 56 and all parts connected to it, including the manually operated work-holder opening or presser-lifting lever 18'and its extension 21.

Also, it is obvious-that when the work-holder is manually opened, the roller stud 62 on the bell-crank lever 56 will be movedto the right to a position close to the full line position of the link 58 and will thus block the movement position while the work-holder is-open.

The needle-loop detaining and severing device comprises a pair of superposed pointed blades 63, 64 secured by the screw 65 to the lever 66 which is fulcrumed on the stud 67 of the bracket-piece 68 screwed to the under side of the table plate 69 on which the throatplate .14 is mounted. The table-plate 69 has a shank 70, Figs. 1 and 18, by which it is secured to the work-supporting arm 2 of the sewing machine frame. The underlappingblade 64 is the loop-detaining blade'and its function is to enter the last needle-loop being drawn out by the shuttle 21, as shown in Fig. 7, following which such loop is drawn up by take-up to a position snuglyembracing the loop-detaining blade 64 and the, bobbinthread 6, as shown in Fig. 8. The overlapping-blade 63 is provided with a curved thread-deflecting edge 71 leading to a cuttingedge 72. The function of the blade 63 is to deflect or guide the work-limb of the needleloop to the cutting edge 72 which, inthe final movement of the blades 63 and 64, severs the work-limb of such loop in cooperation with the sharpened extremity of the ledger-blade 73; such ledger-blade being mounted on the under side of the throat-plate 14, as shown in Figs. 10 and 13.

The lever 66 with its blades 63 and 64 is designed to operate with a two-stage movement, the first stage of which is automatically.

imparted to the lever 66 and the secondstage of which is derivedfrom a manual operation after the machine comes to rest. The first or automatic stageof movement-of the lever 66 is derived from the trailing inclined end 74 of a cam-plate 75 mounted on the cam 27. The cam-plate 75 cooperates-with the rollerstud 76 on the upper end of the lever .77 fulcrumed at 78 to the sewing machine frame.

' The lever 77 is connected at its lower end by means of a ball-and-socket joint 79 toone end of a yieldingly compressible link 80 the other end of which; is connected by the balland-socket joint 81 to the lever 66. The linkv 80 includes the tubular member 82 which houses the compression spring 83 and is entered by the plunger 84 having a shoulder 85 which bears against the spring 83. Thelun er 84 carries a crossin 86 workin in guide-slots 87 in the tubularmember 82. A

spring 88 coiled about the fulcrum-screw 78 bears at one end against a screw-pin 89 on the lever 77 and yieldingly urges such lever in a direction to carry the roller-stud 76 toward the cam-disk 27. The other end of the spring 88 is anchored to. a stud-pin 90 fixed to the sewing machine frame. The stop-motion lever 32 is connectedto the lever 77 by means the lever 77. J. of the stop-motion lever 32 to its'running The operation is as follows When the stop-motion'lever .32 is tilted to dotted line or running; position, Fig. 1,. the link 91 pushes the lever 77 to dotted line position and thereby moves the needle-loop detaining and severing blades 63, 64 from full to dotted line positions,,Fig. 5. This movement of the lever '77 shifts the roller 76 slightlyv out or range of the cam-plate 7 5,so that said roller 76 will not beacted upon by the cam plate 75 when the latter passes under the roller 76 at the end of the first orv secondrevolution of the 7' cam 27. y 1 1 I When the stop-motion lever 32 is finally released by the movement of the roller 39 into the notch 40 in the cam 26, the cam:

plate 7 5 is under theroller 76, as shown in r Fig. 17, and prevents the lever 77 from moving out of its dotted line position,Fig. 1, under the influence of the spring 88. Hence '1 the needle-loop detaining and severing blades 63, 64 remain in their dotted line positions, Fig. 5, when the'stopsmotion lever32 is released and moves as its vertical or stopplng position, Fig. 1. During the-last re-volution of the main-shaft 24 and while the stop-cam 30 is depressing the plunger-bar 31 preparatory to the final ascent of the plung er bar 31 into the stop-notch in the cam 30,

the trailing inclined end 74 of the camplate 75 passes beyond the roller 76 and allows the lever-7 7 to be moved by the spring 88 from dotted line position, Fig. 1, to full line p'osi 1 tion, whereby theneedle-loop detaining and V a drawn out by the shuttle, as shown in Fig. 7

and detains such loop, as shown in Fig. 8, when the machine comes to rest. a

l/Vhen the operator exerts a down-pull on V the lever-arm 21 to raise the bar 6 andpresser-foot 8 or, in other words, manually opens the work-holder for removal of the I work, the bobbin-thread cutter-bar 51* is manually projected toward the free end of the work-supporting arm 2, as previously eX- plained. During this movementot the bar 51, the block 95 strikes the lever 66 andmoves the latter from the full line position-shown 1 in Fig. 5, to the. position shown in Fig. 6, thereby causing thework-limb of the detained needle loop to be deflected bythe curvededge 71' of the blade 63to the cutting edge 72 which cooperatesjwith the ledgerbiade 73 to sever such work limb substantial;

ly simultaneously with the severing of the bobbin-thread by the cutting edge 52. This last described movement of the blades :63, 64

which is caused by the impact of the block 95 upon the lever 66, is the manually efieoted second stage movement of the needle-loop detaining and severing device. This movevision is made for the severing of both the needleand bobbin-threads, without encuinbering the presser-member of the work-holder and the superstructure of the machine with the various small parts of a thread-cutting mechanism such as shown-in the Barron et al. patent previously referred to. The mecha nismvis simple and is readily applied to a machine of the type shown insaid Barron et a1, patent. 1 x

c The second cam-plate on the cam-disk 27 is'in the nature of a safety device to prevent actuation of the blades 63, 64 in the early stage of a stitching cycle, in case the stopm'otion lever 32 is, for any reason, not properly retained in running position when the inclined cam nose 4L5 passesthe tail-pin 46.

Having thus set forth the nature of the invention, what-I claim herein is 1. A sewing machine having, alreciprocat- 1 ing needle, a bobbin, a throat-plate, a stopdetained needle-loop.

motion mechanism, a needle-loop detaining and severing implement pivotally mounted below said throatplate, automatic means timed to impart a first stage of movement to said implement about its pivot to cause the latter to enter and detain the last needleloop, a manually operated bobbin-thread pulloff and severing device, and an operative connection between said manually operated-bob.

bin-thread pull-off and severing device and said needle-loop detaining and severing implement, whereby the manual operation of said device imparts a further movement to said implementabout its pivot to sever the 2. A sewing machine having, a reciprocating needle, a bobbin, a throat-plate, stopmotion' mechanism including: a control lever shiftable between running and stopping positions, a needle-loop detaining and severing device below said throat-plate, automatic means timed to impart a first stage of movement to said device to cause the latter to engage and detain the last needle-loop,manually operated means for imparting a second stage of movement to said deviceto cause the latter to sever said'needle-loop, and means connected to said stop-motion lever to restore said needle-loop detaining and severingde vice to initial position whencsaid'lever is shifted to'running position, c

3. A sewing machine having, in combination, a reciprocating needle, abobbin, stop motion mechanism, a reciprocating bobbinthreadipull-off and severing device, manual means for operating said device,an oscillating needle-loop detaining and severing implement, automatic means for pro]ecting said implement into the last needle-loop to detain the latter, and means on said device for imparting a further movementto saidimple ment to sever the needle-loop concurrently with the severance of the bobbin-thread.

4:. A sewing machinehavinga reciprocating needle, a bobbin, a throat plate, a reciprocatingbobbini-thread pull-off and severing implement mounted below said throat-plate, and a pivotally mounted needle-loop detaining and severing implement disposed below said throat-plate and above said bobbinthread pull-off and severing implement.

5. A sewing machine having, a reciprocat ing needle, a bobbin, a throat-plate, a reciproeating bobbin-thread pull-0E and severing implement mounted below said throat-plate, and a pivotally mounted needle-loop detaining and severing implement disposed below said throat-plate and above said bobbinthread pull-off and severing implement, automatic means for imparting a first stage of 'movement to said needle-loop detaining and for movement independently of one-another,

automatic means for pivotally moving said needle-loop 'cutter'to detain the last needle thread loop, and manual means for moving said bobbin-thread cutter to sever the bobbinthread and for further pivotally moving said needle-loop cutter to sever the detained needle-loop; I v

c 7. In a lock-stitch cylinder-bed sewing machine, the combination with the frame including the cylinder-bed and overhanging arm, of stitch-formingmechanism incorpo rated in saidframe and including a rec1pro-;

eating needle and complemental loop-taking means, a stop-motion device, a bobbin-thread pull-off and severing device'including a manually operated slide-bar mounted for endwis'e reciprocatory movements lengthwise of said cylinder=bed, a'needle-loop detaining and severing device pivotal l y mounted at the free end of said cylinder-bed, and automatic means for imparting a first stage of pivotal movement to said needle-p detaining and severing device to cause it to enter and detain the last needle-loop, said slide-bar being adapted to engage and impart a further pivotal movement to said needle-100p detaining and severing device to cause the latter to sever the detained needle-loop When the bobbin-thread is severed.

In testimony whereof I have signed my name to this specification.

ALBERT F. FIFIELD. 

